For those that don't know:
It was a jump-scare flash game.

The goal was to navigate through the maze with your mouse, without touching the walls, which gets harder near the end, likely resulting in you getting closer to and concentrating hard on the screen.

Near the end they flashed a horror image and blasted a loud sound through your speakers.

Personally, it didn't make me flinch much though,
but I guess it affected some others like OP.